1. Field of the Invention
This invention relates generally to vacuum cleaner nozzles, and more particularly to a generally rectangular vacuum cleaner nozzle having a slightly concave or flat main body portion with a central exhaust aperture for connection with a vacuum hose wherein the main body portion is maintained a predetermined distance above a flat surface to be cleaned and is configured to draw air between the surface to be cleaned and the bottom surface of the nozzle at a substantially uniform velocity which is proportional to the inflow velocity of the vacuum hose, and to maintain little or no difference in static pressure between the air under the nozzle and the static pressure of the air above the nozzle.
2. Brief Description of the Prior Art
A common problem with commercially available vacuum cleaner nozzles for heavy duty use, such as those used with a "Shop-Vac", is that they tend to grab the surface being vacuumed, for example when attempting to vacuum leaves off of a patio. The present vacuum cleaner nozzle has a novel configuration that was developed as result of careful testing of various prototypes.
Early testing was carried out using a board not much larger than the large diameter handheld flexible hose of a homebuilt garden vacuum. The board was equipped with 4 small full-swiveling wheels serving as spacers to place the board a distance above the ground and for ease of guidance and manipulation. It was discovered that the board itself was improving the vacuum performance of the system.
Subsequent use in my woodworking and metalworking shop revealed many problems including: rapid wear of the four supporting knobs or feet, difficulty in replacing those feet, their susceptibility to being broken off on irregular surfaces, inability to determine whether short wires, BB's, glass, or other dangerous objects had been picked up or moved to an undetermined location.
Another problem was the lower rate of flow at the corners than other locations. Early tests were made primarily by visual observations rather than using airflow instruments, such as commercially available normal and ultra-light aircraft speed indicators, since these types of instruments were ineffective in the limited space and airflow velocity of the vacuum cleaner. However, later qualitative practical testing was carried out to test the effectiveness and relative velocities using BB's and iron filings as the materials to be picked up and using an aircraft altimeter to measure the static pressure about a flush mounted probe as the nozzle was moved about it.
These tests revealed that conventional prior art vacuum cleaner nozzles are designed such that a very high velocity exists at their outer edges, but the larger volumes downstream of the edges act as a large volume plenum chamber in which the actual velocity is diminished, thus reducing the ability to move debris to the pick-up point of the nozzle.
The aerodynamic design of the present invention produces a uniform velocity from all points into the pickup point (the central aperture which is connected with the hose). This may be demonstrated by sprinkling coarse iron filings on a hard floor, placing the nozzle over them and observing the flow of the filings when the vacuum is applied. After the flow has stabilized for a couple of seconds the filings are gone from beneath the nozzle and for about 1/4 inch outside of the nozzle perimeter. Similar testing shows that small BB's and shotgun shot perform similarly.
Commercially available nozzles of the prior art are unable to effectively remove dense objects such as BB's and shot, etc. Instead, they move debris from the high velocity area near their outer edges, but leave it collected under the nozzle in the low velocity areas of the pickup point (the central aperture which is connected with the hose). Typically, prior art nozzles are designed to achieve a high pressure differential with the resultant increase in air speed near their perimeters but at a loss of air speed inwardly from their perimeter brushes and walls. As a result, they can suffer loss of air speed and flow rate if the operator does not properly control the position of the nozzle.
The present invention is distinguished over the prior art in general by a vacuum nozzle adapted for use on a working surface that has a generally rectangular main body portion with a top surface, a bottom surface, an outer periphery, and a central aperture through the main body portion for connection to a vacuum hose connected to a vacuum source. The main body portion may be slightly concave or flat. Spacers on the bottom surface support the main body portion above a surface to be cleaned at a predetermined height. The size and shape of the bottom surface, and its height above the surface to be cleaned are designed to draw air between the surface to be cleaned and the bottom surface of the nozzle at a substantially uniform velocity which is proportional to the inflow velocity of the vacuum hose connected with the nozzle, and to maintain little or no difference in static pressure between the air under the nozzle and the static pressure of the air above the nozzle.